>>76312626Human Body Temperature Decline
Recent studies have shown that human body temperature has been decreasing over the past two centuries. For example, analysis of three U.S. cohorts spanning almost two centuries revealed a 0.03°C decline per decade in normal body temperature (BT) of adults, leading to an inference that humans in high-income countries currently have a mean body temperature 1.6% lower [36.4°C] than in the pre-industrial era.
Similarly, a study analyzing 677,423 human body temperature measurements from three different cohort populations spanning 157 years of measurement found that men born in the early 19th century had temperatures 0.59°C higher than men today, with a monotonic decrease of −0.03°C per birth decade.
This decline has also been observed in women, with a decrease of −0.32°C since the 1890s and a similar rate of decline (−0.029°C per birth decade).
The generality of this phenomenon and the reasons behind it have not yet been well studied, but factors such as reductions in infectious disease, changes in physical activity, body composition, antibiotic usage, and thermal environment are potential causes.